The present invention relates to a method for providing a quantity representing the longitudinal inclination of a vehicle, and/or a signal representing the longitudinal inclination of a vehicle, for a control unit for the slip control of the vehicle or a control unit for the control of a quantity describing the yaw rate of the vehicle. The present invention also relates to a control unit for the slip control or for the control of a quantity describing the yaw rate of a vehicle, as well as a control unit for controlling the headlight level of a vehicle, having means for generating and processing a quantity and/or a corresponding signal representing the longitudinal inclination of the vehicle. To be understood by the headlight-leveling control is the control of the headlights, in particular the low-beam headlights, provided on a vehicle.
Headlight systems of modern motor vehicles are frequently designed with xenon gas-discharge lamps as a central component (Litronic system). Such lamps have high lighting effectiveness, accompanied by the least front-area requirement. Because of legal regulations, such xenon lamps must be equipped with automatic headlight-leveling control. For that purpose, using Hall sensors for example, it is possible to perform measurements of the spring-deflection depth at the front and rear axle of the motor vehicle. In doing this, the Hall sensor measures the twisting of a torsion bar or a stabilizer that is in operative connection with the front and rear axle, respectively. The longitudinal inclination of the vehicle is detected by the use of two such measuring points. Thus both a spring deflection in the rear-axle area produced by loading (static spring deflection), as well as a spring deflection caused by pitching such as during a braking operation (dynamic spring deflection) are taken into account in the headlight-leveling control.
German Patent Application No. 197 04 427 describes a device for controlling the headlight level (light range) of vehicle headlights having adjusting devices, allocated to the headlights, for adjusting the headlight level, with a transmitting device used for emitting at least one electromagnetic beam of light which illuminates an area in front of the vehicle. The device also has an opto-electronic sensor device in which at least the one illuminated area is imaged as a pixel, as well as an evaluation device which evaluates the position of the at least one illuminated area, and from this, forms a signal which is compared to a setpoint signal representing a correct setting of the headlight level. In response to a deviation between the prevailing signal and the setpoint signal, the adjusting devices are driven to eliminate the deviations, the position of the at least one pixel in relation to at least one reference position in the sensor device being evaluated by the evaluation device, and a signal being formed for it.
German Patent No. 23 33 983 describes a device for controlling the level of vehicle headlights. This device has a sensor device in the area of the front axle and in the area of the rear axle, respectively, which at least indirectly detect the change in position of the vehicle in the region of the front axle and rear axle with respect to the roadway. In this case, the sensor devices are ultrasonic sensors which have a sensor and a receiver. Ultrasonic radiation is emitted toward the roadway by the sensor, and ultrasonic radiation reflected at the roadway is detected by the receiver. The ultrasonic sensors are connected to an evaluation device which, from the signals of the sensors, determines the respective distance of the sensors and thus of the vehicle bodywork from the roadway. The evaluation device determines the inclination of the vehicle based on the distance of the sensors at both axles, and drives the adjusting devices allocated to the headlights in such a way that the headlight level is kept at least approximately constant regardless of the vehicle inclination.
The use of spring-deflection-path signals is also known in connection with anti-lock and traction control systems (ABS/ASR systems). For example, German Patent No. 43 40 442 describes an anti-lock and/or traction control system, in which the brake pressure is varied as a function of the wheel-movement behavior along the lines of avoiding locking or a free spinning of the driven wheels, and a signal which represents the nature of the roadway surface is also supplied to this system, this signal effecting a change in at least one control parameter within the control system. According to this document, spring-deflection-path signals are used in particular as the signal (unevenness measure) representing the roadway surface.
A disadvantage in the case of customary motor vehicles is that, for reasons of cost, only estimation quantities for the longitudinal inclination of the vehicle are used for control devices for regulating slip or for regulating a quantity describing the yaw rate of the vehicle. A continuous provision of prevailing measured quantities which accurately and reliably represent the longitudinal inclination of the vehicle is unknown in such systems.
An object of the present invention is to provide a cost-effective possibility for supplying accurate, current-status measured quantities with respect to the longitudinal inclination of the motor vehicle to control devices for slip control (ABS and/or ASR) or for controlling a quantity describing the yaw rate of the vehicle (operating-dynamics control FDR or electronic stability program ESP).
This objective is achieved by a method for providing a signal, representing the longitudinal inclination of a vehicle, for a control unit for slip control and/or for controlling a quantity describing the yaw rate of the vehicle. Measured quantities which can be acquired and processed for ascertaining a signal representing a longitudinal inclination of the vehicle, and/or the ascertained signal representing the longitudinal inclination are/is transmitted by a control device for the headlight-leveling control to the control unit for the slip control and/or for the control of the quantity describing the yaw rate.
According to the present invention, it is possible to transmit quantities describing the longitudinal inclination of the vehicle, which can be acquired and processed by a control unit for the headlight-leveling control of the vehicle, or a signal which represents the longitudinal inclination of the vehicle and is generated from these measured quantities by the control unit for the headlight-leveling control, to an operating-dynamics system (slip-control system and/or system for controlling a quantity describing the yaw rate of the vehicle) and to use them there to improve the control. The following influence possibilities, which can be optimized with the aid of such information about loading or inclination angle, are named by way of example: The information about the longitudinal inclination is usable in reference value generation, i.e., in determination of the vehicle velocity over ground (over road surface traveled), in particular for vehicles which, in the drive case, utilize information about the output engine power (4-wheel vehicles). In this case, due to the information about the loading or the longitudinal inclination of the motor vehicle, the engine output can be set in an improved manner in a relation to the propulsive power. In addition, in the case of an ABS braking, the dynamic axle-load shift, and thus the change in the wheel load, can be estimated using the information about the longitudinal inclination. Thus, it is possible to guide the operating point of the ABS controller more quickly to its optimum, such as in the case of a sudden change in the coefficient of friction.
Inferences can be drawn about uphill or downhill grade using the information about the inclination angle of the vehicle existing when the vehicle is at rest, thus permitting optimization of the operating point of an ASR/ABD system during a start from rest. ABD denotes an automatic brake differential. Furthermore, utilizing the constantly updated information about the longitudinal inclination, the brake-application performance can be improved by a pressure build-up adapted to the change in the wheel load. Due to this, it is possible to attain a reduction of pitching vibrations, and thus a reduction of the braking distance and an improvement in comfort accompanying this.
According to the present invention, it is also possible to undertake a correction of mass in the case of physical control formulations. The method of the present invention offers support when determining the optimum braking-force distribution, as well as a correction of the reference gradient during brake application. Plausibility relationships with respect to the wheel performance, and thus an optimization of the vehicle reference value in drive and braking processes, are also ascertainable.
According to one advantageous refinement of the method of the present invention, the depths of the vehicle spring deflection in its front and rear axle area are used as the measured quantities representing the longitudinal inclination of the vehicle. The spring-deflection paths thus ascertained and/or the loading or longitudinal-inclination information determined on the basis of the spring-deflection paths are easily transferable to an operating-dynamics system.
Hall sensors which measure the twisting of a torsion bar or stabilizer are expediently used to ascertain the spring-deflection depths. Very precise and reliable measuring results can be obtained with these means.
According to another preferred specific embodiment of the method of the present invention, gradient sensors are used to determine the quantities representing the longitudinal inclination of the vehicle. Such sensors prove to be very sturdy and reliable.
The object underlying the present invention is also achieved by a control unit for the slip control and/or for the control of a quantity describing the yaw rate of a vehicle, the control unit including means for the reception and processing of measured quantities, from which a signal can be ascertained representing the longitudinal inclination of the vehicle, or for the reception and processing of a signal determined on the basis of this measured quantity and representing the longitudinal inclination of the vehicle, from a control unit for the headlight-leveling control.
The object underlying the present invention is further achieved by a control unit for the headlight-leveling control of a vehicle, having means for acquiring measured quantities, based on which a signal can be determined representing the longitudinal inclination of the vehicle, and having means for generating a signal representing the longitudinal inclination of the vehicle on the basis of the acquired measured quantities, the control unit including means for transmitting the acquired measured quantities and/or the generated signal to a control unit for the slip control and/or for the control of a quantity describing the yaw rate of the vehicle.
By providing the control units of the present invention for the slip control or for the control of a quantity describing the yaw rate of the vehicle, and for the headlight-leveling control of a vehicle, it is possible to use existing measured quantities or signals with respect to the longitudinal inclination of the vehicle for two different functions of a motor vehicle. By this means, both functions, namely the slip control and/or the control of a quantity describing the yaw rate of the vehicle, and the headlight-leveling control can be optimized while saving on sensor components and computing expenditure, without additional outlay.